Fused filament fabrication (FFF) of thermotropic liquid crystal polymers (LCPs) presents an attractive route toward lightweight components with excellent in-plane mechanical properties, enabled by molecular alignment during extrusion. However, the layer-by-layer nature of FFF leads to weak interlayer adhesion, which severely compromises mechanical performance in the build direction (Z-axis). This anisotropy limits the structural reliability of printed LCP parts under demanding conditions. Inspired by through-thickness reinforcement methods used in laminated fiber-reinforced composites, this thesis investigates the potential of z-pinning to enhance interlayer strength and damage tolerance in FFF-printed LCPs.

This work focuses on adapting the z-pinning concept, previously applied in PLA systems, to the challenges of anisotropic, shear-aligning LCPs. A z-pinning methodology is developed around the commercial filament Vectra® A950, utilizing a bottom-up insertion process enabled by custom G-code routines. Vertical pins are extruded into pre-formed voids during the print, allowing control over pin shape, height, and placement. The approach leverages standard FFF hardware, requiring only a narrow-tip nozzle and careful synchronization of extrusion timing to ensure consistent pin deposition.

Mechanical testing was conducted on both pinned and unpinned tensile specimens printed in the Z-direction. The results demonstrate that z-pinning significantly enhances performance when properly implemented. The best configuration, tall pins arranged in an ABA staggering pattern, achieved a 40% increase in peak load and a tenfold increase in energy absorption before reaching peak load. Fracture analysis revealed more distributed fracture patterns, with signs of crack deflection and arrest, indicating a transition from brittle delamination to
more progressive failure modes.

These findings validate the feasibility of z-pinning for improving the mechanical properties of 3D-printed LCP components. However, the benefits are highly sensitive to process execution, as poor pin deposition may negate reinforcement or introduce stress concentrators. The study underscores the importance of concurrent design and manufacturing development, showing that even in single-material systems, structural performance can be engineered through localized deposition strategies. This opens a path toward more robust, anisotropy-mitigated 3D-printed parts using high-performance polymers.